Joint lock hammer



July 20, 1965 Filed May 25, 1962 A. M. ERICKSON 3,195,492

JOINT LOCK HAMMER 2 Sheets-Sheet l AT'TO RNEYs July 20, 1965 A. M. ERICKSON 3,195,492

JOINT LOCK HAMMER Filed May 23, 1962 2 Sheets-Sheet 2 INVENTOR. Afifi/Wr M Elle/r50 M fM ATTORNEYS 3,195,492 JOINT LOCK HAMMER Arthur M. Erickson, 1413 Jackson St Seattle, Wash. Filed May 23, 1962, Ser. No. 197,825 13 flaims. (Cl. 113- 54} This invention relates to a hammer and more particularly to a power hammer designed to close a sheet metal joint commonly known in the trade as a Pittsburgh lock.

It is a general object of this invention to provide such a hammer which is of simple and economical, and yet durable construction, which is adapted to operate easily and ehiciently on either heavier or lighter gauge sheet metal, and which will close such a metal joint without scuffing or otherwise damaging the sheet metal surface, and without distorting or bending the metal which forms the joint or which is adjacent thereto.

It is a further object to provide such a hammer which is readily adapted to be made as an attachment to any number of standard prior art rotary power tools, such as a portable bench grinder. Other more particular objects and advantages of the invention will, with the foregoing, appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

1 In the accompanying drawings:

FIGURE 1 is a fragmentary front elevational view showing a hammer made in accordance with my invention, the hammer being shown in operating position to bendover the outstanding edge of one metallic sheet so as to lock the joint;

FIG. 2 is a fragmentary view, drawn to an enlarged scale and taken on line 22 of FIG. 1, thus showing the hammer in side elevation and showing the sheet metal joint in section;

FIG. 3 is a side View of one embodiment of my invention, with the side cover of the housing removed to show the working parts therein;

FIG. 4 is a fragmentary sectional view taken on line 4-4 of FIG. 3 and drawn to an enlarged scale;

FIG. 5 is a view similar to FIG. 3, but showing a second embodiment of my invention;

FIG. 6 is a view similar to that of FIG. 5, but showing yet another embodiment of my invention; and

FIG. 7 is a fragmentary sectional view taken on line 7-7 of FIG. 6.

It is believed a clearer understanding of the nature, operation, and advantages of my invention will be attained by first describing in some detail the Pittsburgh lock and the manner of closing the same, and commenting briefly on the prior art machines devised to accomplish this operation and the difi'iculties encountered in the use of such prior art machines.

The Pittsburgh lock has long been used widely in the I sheet metal industry in fastening opposite edges of one sheet of metal together, or two edges of different sheets of metal together, at a corner line of a duct or other structure. The sheets to be joined each have their edge portion prefabricated in a particular manner. One such sheet 19 has its edge portion bent at a right angle to form a downturned flange portion 11, this sheet being designated as the angled sheet. The other sheet 12, called the replaite'd' sheet, has its edge portion folded back on itself to form a fiat S fold, the inner, middle and outer portions of this fold being designated 13, 14 and 15, respectively. The middle and outer folds 14 and 15 are spaced slightly one from another to form an upwardly facing channel or groove 16 to receive the downturned flange 11. The outer fold 15 has its upper end portion extending beyond the United States Patent 0 folds 13 and 1 to form an upstanding flange 17, commonly called the outstanding edge. In forming the Pittsburgh lock, the downturned flange 11 is inserted into the channel 16, and then the outstanding edge 17 of the replaited sheet 12 is folded flat against the portion of the angled sheet 16 just inside the bend along a seam line 18. This completes or closes the lock so as to hold the two sheets together.

Clearly, manually hammering the outstanding edge 17 against the angled sheet is a time-consuming and hence inefiicient operation. To perform this function mechanically, the prior art oifers a number of devices. Some of these are designed to ride along the seam of the joint and press the outstanding edge into its lock position. Others have a reciprocating hammer motion and have the hammer head formed with its contact surface so curved that as the hammer is moved progressively along the seam, different portions along the hammer surface will pound any one portion of the outstanding edge over by incremerits.

The difficulties encountered with the prior art devices are several. Aside from the fact that most of the devices are unduly complex and hence too expensive for the more limited needs of many users, a good number of these are designed for only a relatively limited range of metal thicknesses. Thus if used on too heavy a metal, the machine is simply underpowered, and if used on too light a metal, the metal around the jointed area is bent or pounded out of shape. Another problem, which is encountered especially with machines having a reciprocating hammering motion, is that a machine which is small enough and light enough to be used conveniently by one man, is often not sturdy enough to endure extended and hard usage without requiring a good deal of expensive maintenance. Also in many of these machines, if not used skillfully, the galvanized finish, especially on the outstanding edge, becomes scufied, besides causing the metal near the joint to become bent or distorted.

Thus the apparatus of the present invention was devised to accomplish the aforestated objects of the invention so as to solve these problems.

Referring to the accompanying drawings, a standard prior art rotary tool, such as a bench grinder, is shown schematically at 21 this tool having a nose portion 21 with a power driven shaft 22 extending laterally therefrom. The hammer portion 25 of my invention comprises a closed housing structure 23, having the general configuration of a shallow cylinder. The curved circumferential wall of this cylinder-like housing is designated 24, while the flat circular side plates are designated 26 and 27, respectively, the latter being removably secured to the curved wall 24 by means of bolts 28. Extending outwardly from the center of the side wall 26, is a boss 39, having a center opening 31, to accommodate the shaft 22 which is inserted therein. So that housing 23 may be rigidly secured to the rotary tool 20, an angle iron 32 is welded or otherwise secured to the housing, and is bdlted, as at 35, to the rotary tool.

Carried in the housing 23 for rotary motion therein is a flat circular drive plate 34, having a diameter moderately less than that of the inside surface of the cylindrical housing wall 24. At evenly spaced intervals along the circumference of the plate 34, are a plurality of semi-circular pockets 36, each arranged to interfit loosely with a related one of an equal number of hard, metallic, spherical balls 37 of uniform size. An internally threaded nut 38 is welded or otherwise secured to the center of the plate 3 to provide a socket to receive the threaded end of the power shaft 22, so that the plate 34 may be rigidly secured thereto.

The inner surface of the cylindrical housing wall 24 is formed with a rounded circumferential groove 40, having a radiusof curvature slightly 7 the balls 37. Thus as the'plate '34 is rotated by the power shaft 22 within the housing 23, the balls 37, each in its related pocket 36, are caused to roll in a circular path within 'the race defined by this groove 40. v g

The lower end ofthe housing (i.e. the position of the portion of the housing furthest from the rotary tool 20) is formed with a re-entrant right angle cutout 41. The short-side surface '42 of this cutout extendsradiallyin ward toward the center of rotation of the plate 34 '(the plane of this surface thus being at right angles to thecircumferential path of the groove at this point), and

extends into thegroove 40 to a distance substantially less 7 than the radius of any one of the balls37. The long side surface 43 f this cutout extends from the inner edge .44

of the surface 42- at right angles thereto,2the direction of I greater than the radius of related one .of four balls 37 It is "believed thatlthe invention will have been clearly understood from the vforegoing detailed description of my this extension being the same direction of travel of the plate 34 -at,this point. The effect of forming such a cutout is that as the balls 37 pass thereover each ball moves into the cutout bypassing through the plane of the cutout surface 42, 'in a manner that'the outer portion'45 of each ball protrudes a short distance into this cutout (i.e.- beyond the plane, defined'by the cutout surface 43').

The width of the cutout 41 is less than the diameter of the ballsto prevent the balls from 'escapingtherethroughs In' operation, the housing structure 23 'isfsecure'd to the rotary tool 20 by bolting the'an'gle iron 32 to the rotary tool while slippingthe power'shaft 22 into thebo'ss 30 through the opening 31. The side cover plate 27 is removed, andthe rotary plate 34 is secured" to the shaft 22 by rotating this plate 'so that the nu t 38 (being welded to theplate) threads onto the end of the shaft. (The threads are so arranged that as the plate 34 rotates, the action of such rotation is to thread the nut :38 more tightlyonto the shaft. A stop collar 461s welded to the shaft 22 to limit the extent to which it threads into the nut 38.) The cover plate 27 is again bolted into place,

and the hammer is ready for operation. I

The do'wntumed flange 11 of the angle sheet 10, is insorted into the channel-16 of the edgeportion of the now-preferred illustrated embodiments; Changes in the details of construction may be resort edto without 'departing from the spirit of the invention and it is-acc'ordinglyj my intention that no limitationsbe'implied and that the 1 hereto annexed claims be given the broadest interpretation to which the employed language fairly admits.

Whatl claim is:

1. A hammer to fold over the-outstanding edge of a metal joint in a manner to close the joint, said hammer comprising:

replai-ted sheet 12 with the outstanding edge 17 're'achihg' I above the top surface of the angle sheet-10. Initially, a portion of the outstanding edge 17 (preferably-an end portion) is manually or otherwise'turned down over the angle sheet 10. The hammer is "then positionedwith the shorter surface 42 of the cutout 41 hearing against the upper vertical-.portion of the outer fold 'lS. Thus the apex line 44 of the cutout surfaces 42 and 43 coincideswith the bend line 18 of the downtu'rnederid portion of the outstandingedge 17. The hammer is then tilted'to a moderate degree away from the intended direction of travel (as shown in FIG. 1) and then moved along the length of the joint. As the balls 37 roll by the cutout 41, each ball impinges on'the outstanding edge 17 so asto fold the outstanding edge against the sheet 10. It -.Will be noted that the lower. point of each ball passes very close to the plane of the top surface of the outstanding edge 17 after it has been folded'into its closed position. The as feet of this is that the outstanding'edge' portion 47 immedie" ately in front of the path of travel of the hammenfby virtue of the edge portion immediately adjacent being, folded over, is caused to be bent a moderate distance' toward its fold position. That is to say, by the time thehammer actually reache any one portion 'of the outstanding edge, that portion has already beenfolded over to some degree. 7 Y

Because of the rolling action of the balls moving along theinn'er' race 40, there is no scuffing action on the exposed surface of the outstanding edge .17." Unless the metal isof-an unusually heavy gauge relative to the size of the tool being used, one the jointsecurely.

pass, is generally sufficient 'to lock I I6. 5shows a second embodiment of my invention wherein the plate 34 is replaced by a member 48 having four equally spaced radial arms 49 each of which causes a race in a manner that said Contact 'membe'r will v V protrude into said cutout as it travels alongsaid race,

( d) drive means insaid housing member to travel along saidr'ace, wherebythe hammer' may be located in a manner that said outstanding edge reaches into said cutout, causing'the'contact member to impinge on said outstanding edge so as to fold said edge inte locked position. 1

-' 2. The hammer as recited in claim 1, wherein said contact member is symmetrical about an axis so that said member is caused to roll along said race. a

3. The hammer as recited in claim 1, wherein said contact member is a spherical ball and said race is defined by the inner surface of a cylindrical wall of said housing.

4. Thehammer as recited in claim'3, wherein said drive means is a member mounted in said housing for rotary motion therein, said rotary member acting to contact said ball and push said ball along said race.

5 A hammer to fold overthe outstanding edge of a metal .joint in a manner to close the joint, said hammer comprising: I

(a) a housing having a cylindrical wall, the inner surface of which defines acir'cumferential race,

(.b) a cutout in said housing, said cutoutextending into the path of said race,

(c) a plurality of rolling members carried-in said (e) :power means to rotate "said drive member, so that bylocating said housing with the outstanding'edge in said cutout, said rolling members are causednto impinge 'on'said outstandingedge so as to fold said I e'dge'overto lock thejoirit; e I

6. The 'hammeras recited inclaimS, wherein said drive .member is'a plate having aplu'rali-ty of circumferential'pockets, each pocket to receive a relatedoneof said rolling members.

7. The hammer'ajs recited in claim :5; wherein said drive member hasa plurality of -arms',"e'ach or said arms to 8. The hammer as recited in:claim 5, wherein power means is a rotary power toolhaving a drive shaft to turn said drive'member, said housing having means by to cause said contact said i 9;. The hammer as recited in claim 5, wherein said cutout has a surface the plane of which is at substantially right angles to the path of said race, so that by causing said cutout surface to bear against the joint surface below the outstanding edge, said hammer properly is located with respect to said joint so that the outstanding edge may be properly folded to close the joint.

18. The hammer as recited in claim 9, wherein said race is a rounded groove, and each of said rolling members is a spherical ball arranged to roll in said groove.

ill. A joint lock hammer comprising:

(a) a housing defining an annular race on the inside surface thereof,

(b) at least one contact member located in said race in engagement therewith,

(c) means to move said member along said race,

(d) and a cutout in said housing intersecting said race and adapted to receive a portion of a sheet metal joint in the path of said contact member.

12. The hammer according to claim 11 wherein:

(a) said cutout is in substantially right angular form,

(b) said cutout having a short side extending radially with said annular race, and extending into said race a distance less than the thickness of said contact member,

(0) and a long side extending in the direction of travel of said contact member.

13. A hammer for closing a Pittsburgh lock between an angled sheet-metal member and a replaited sheet metal member having an outstanding edge comprising:

(a) a housing having a continuous annular groove on the inside surface thereof forming a circular race, (b) a cutout in the outside surface of said housing and intersecting said groove and adapted to receive a bent portion of said outstanding edge,

(e) at least one contact member positioned for travel in said groove in engagement therewith,

(d) means in said housing to move said contact member in said groove,

(e) whereby said contact member impinges against the surface of said outstanding edge located in said cutout to fold the same against the outside surface of said angled sheet-metal member.

References Cited by the Examiner UNITED STATES PATENTS 1,034,480 8/ 12 Meadowcrott 78-53 1,240,791 9/ 17 Czajka 113-52 1,467,166 9/23 Jones 78-21 1,842,571 1/32 Sebell 113-52 2,919,611 1/60 Nichols 78-21 CHARLES W. LANHAM, Primary Examiner. 

1. A HAMMER TO FOLD OVER THE OUTSTANDING EDGE OF A METAL JOINT IN A MANNER TO CLOSE THE JOINT, SAID HAMMER COMPRISING: (A) A HOUSING DEFINING A CONTINUOUS ANNULAR RACE, (B) AT LEAST ONE CONTACT MEMBER ARRANGED FOR TRAVEL ALONG SAID RACE AND CONSTRAINED IN A CIRCULAR PATH BY SAID RACE, (C) A CUTOUT IN SAID HOUSING TO EXPOSE A PORTION OF SAID RACE IN A MANNER THAT SAID CONTACT MEMBER WILL PROTRUDE INTO SAID CUTOUT AS IT TRAVELS ALONG SAID RACE, AND (D) DRIVE MEANS IN SAID HOUSING TO CAUSE SAID CONTACT MEMBER TO TRAVEL ALONG SAID RACE, WHEREBY THE HAMMER MAY BE LOCATED IN A MANNER THAT SAID OUTSTANDING EDGE REACHES INTO SAID CUTOUT, CAUSING THE CONTACT MEMBER TO IMPINGE ON SAID OUTSTANDING EDGE SO AS TO FOLD SAID EDGE INTO LOCKED POSITION. 